Processing apparatus

ABSTRACT

A processing apparatus of the invention includes: a processing vessel in which a vacuum can be created; a stage disposed in the processing vessel for supporting an object to be processed thereon; a clamping member supported above the stage and capable of pressing down a peripheral part of the object to be processed mounted on the stage to fixedly hold the object to be processed on the stage; an elastic member for giving a force to cause the clamping member to press down the peripheral part of the object to be processed mounted on the stage; and an elastic-member cover substantially entirely covering the elastic member.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a processing apparatus forconducting a predetermined process to an object to be processed, such asa semiconductor wafer.

[0003] 2. Description of the Related Art

[0004] Generally, in a semiconductor integrated circuit manufacturingprocess, a semiconductor wafer, which is an object to be processed, issubject to various processes including a film-forming process, anetching process, an oxidation diffusion process, an annealing process, amodification process and so on. In a film-forming process, for example,a metal or a metal compound, such as tungsten (W), tungsten silicide(WSi), titanium (Ti), titanium nitride (TiN) or titanium silicide(TiSi), is deposited to form a wiring pattern on a surface of a wafer orto fill up recesses between wiring lines, or an insulating film, such asa SiO₂ film, is deposited.

[0005] A generally known conventional single-wafer processing apparatuswill be described with reference to FIGS. 4 and 5A to 5C.

[0006]FIG. 4 is a schematic sectional view of a generally knownconventional single-wafer processing apparatus, and FIGS. 5A to 5C areschematic sectional views of assistance in explaining the operation ofan object-to-be-processed holding member (clamping ring). Thisprocessing apparatus is provided with a processing vessel 2 in which avacuum can be created. A showerhead 4 for introducing various necessarygases into the processing vessel 2 is incorporated into a top wall ofthe processing vessel 2. A thin stage 8 is supported on a cylindrical,reflective support 6 set on a bottom wall of the processing vessel 2. Asemiconductor wafer W is mounted on the stage 8. A plurality of heatinglamps 10 are disposed under the processing vessel 2. Heat rays emittedby the heating lamps 10 travel through a transparent window 12 attachedto the bottom wall of the processing vessel 2 into the processing vessel2, and heat the stage 8 to heat the wafer W mounted on the stage 8.

[0007] Three lifting pins 16 (only two of those are shown in FIG. 4)attached to a circular lifting ring 14 are arranged to extend under thestage 8. The lifting pins 26 are vertically movable so that they canextend through holes 18 formed in the stage 8 and that can come incontact with a lower surface of the wafer W to vertically move the waferW.

[0008] A lifting rod 22 for vertically moving the lifting ring 14 isvertically extended through an opening formed in the bottom wall of theprocessing vessel 2 and is connected to the lifting ring 14. The openingformed in the bottom wall of the processing vessel 2 is covered with abellows 20. The bellows 20 allows the lifting rod 22 to vertically moveand also prevents leakage of gases through the opening of the bottomwall.

[0009] A circular clamping ring 24 is pressed down to a peripheral partof the wafer W mounted on the stage 8 to fasten the wafer W tot he stage8 during a process. More specifically, as shown in FIGS. 5A to 5C, threerods 26 (only two of those rods are shown) are attached to a lowersurface of the clamping ring 24 so as to extend downward. Guide members28, each of which has the shape of an inverted letter L and is providedwith an opening 30, are attached to the lifting ring 14 in such a mannerthat the rods 26 are extended loosely through the openings 30 of theguide members 28, respectively. Each of the rods 26 is provided with ahead (stopper) 34 at its lower end. Coil springs 32 are wound around therods 26 in such a manner that the coil springs 32 are compressed betweenthe guide members 28 and the heads 34 of the rods 26, respectively.Thus, the clamping ring 24 is always biased (forced) downward byresilience of the coil springs 32.

[0010] Stopping projections 36 project from upper ends of the guidemembers 28 to limit a downward movement of the clamping ring 24 relativeto the lifting ring 14.

[0011] When mounting a wafer W on the stage 8 of the thus formedprocessing apparatus, a conveying arm, not shown, holding the wafer Wtransfers the wafer W onto the lifting pins 16 set at an upper positionthereof, and then the lifting ring 14 is lowered together with thelifting pins 16 in order to mount the wafer W on the stage 8 as shown inFIG. 5B. Then, the lifting pins 16 are lowered further to bring theclamping ring 24 into contact with a peripheral part of the wafer W. Asthe lifting ring 14 is lowered still further, the coil springs 32 arefurther compressed, whereby the wafer W is held securely on the stage 8by the resilience of the compressed coil springs 32.

DISCLOSURE OF THE INVENTION

[0012] The aforesaid processing of a semiconductor wafer uses variousprocess gases including a highly corrosive gas, such as WF₆ gas(tungsten hexafluoride gas) or Cl₂ gas.

[0013] An interior of the processing vessel must be periodically oroccasionally cleaned by a cleaning process using a cleaning gas (etchinggas), such as ClF₃ gas, in order to prevent falling off of unnecessaryfilms deposited on inner surfaces of the processing vessel and therebyproduction of particles. The cleaning gas also may be highly corrosive.

[0014] When such a highly corrosive gas is introduced into theprocessing vessel 2, the corrosive gas flows unavoidably into a spacearound a back surface of the stage 8. Even if a so-called backside gasis supplied into the space around the back surface of the stage 8, thecoil springs 32 of a metal exposed to the corrosive gas may be corroded,and hence corrosion products may be scattered as particles to causemetallic contamination.

[0015] The present invention has been made in view of the foregoingproblems to solve the problems effectively. Accordingly, it is an objectof the present invention to provide a processing apparatus provided withan elastic member for biasing an object-to-be-processed holding member(clamping member) and capable of effectively preventing corrosion of theelastic member.

[0016] This invention is a processing apparatus comprising: a processingvessel in which a vacuum can be created; a stage disposed in theprocessing vessel for supporting an object to be processed thereon; aclamping member supported above the stage and capable of pressing down aperipheral part of the object to be processed mounted on the stage tofixedly hold the object to be processed on the stage; an elastic memberfor giving a force to cause the clamping member to press down theperipheral part of the object to be processed mounted on the stage; andan elastic-member cover substantially entirely covering the elasticmember.

[0017] According to the invention, the elastic member for giving a forceto cause the clamping member to press down the object to be processed iscovered by the elastic-member cover. Thus, the elastic member isprevented from touching any corrosive gas, and hence corrosion of theelastic member can be effectively suppressed.

[0018] Preferably, the elastic member cover is excellentlycorrosion-resistant. In the case, corrosion of the elastic-member coveris also prevented.

[0019] Preferably, the elastic member cover is formed of a materialhaving a low thermal conductivity. Such an elastic-member cover iseffective in suppressing rise of the temperature of the elastic member,and is further effective in suppressing the corrosion of the elasticmember.

[0020] In addition, preferably, the clamping member has a rod extendingdownward from a lower surface thereof, the elastic member is a coilspring surrounding the rod, the rod is provided with a spring stopper ata lower end thereof to support a lower end of the coil spring thereon,and an upper end of the coil spring rests on a clamping-membersupporting member through which the rod extend and which can support alower surface of the clamping member.

[0021] In addition, preferably, the elastic-member cover is formedintegrally with the clamping-member supporting member.

[0022] In addition, preferably, the elastic-member cover also covers thelower end of the rod and the spring stopper.

[0023] In addition, preferably, the clamping-member supporting member isformed integrally with lifting pins capable of moving through the stageand of vertically moving the object to be processed on the stage.

[0024] In addition, preferably, a processing apparatus furthercomprises: a process-gas supply means for supplying a process gas intothe processing vessel, and a heating means for heating the object to beprocessed mounted on the stage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a schematic sectional view of a processing apparatus ina preferred embodiment according to the present invention;

[0026]FIG. 2 is a plan view of a lifting ring and an elastic-membercover;

[0027]FIGS. 3A to 3C are schematic sectional views of assistance inexplaining an operation of an object-to-be-processed holding member(clamping ring);

[0028]FIG. 4 is a schematic sectional view of a conventionalsingle-wafer processing apparatus; and

[0029]FIGS. 5A to 5C are schematic sectional views of assistance inexplaining an operation of a conventional object-to-be-processed holdingmember (clamping ring).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] A processing apparatus in a preferred embodiment according to thepresent invention will be described with reference to the accompanyingdrawings.

[0031]FIG. 1 is a schematic sectional view of a processing apparatus ina preferred embodiment according to the present invention, FIG. 2 is aplan view of a lifting ring and an elastic-member cover, and FIGS. 3A to3C are views of assistance in explaining an operation of anobject-to-be-processed holding member (clamping ring).

[0032] A processing apparatus 40 has a cylindrical or box-shapedprocessing vessel 42 made of, for example, aluminum, in which a vacuumcan be created by evacuating. A cylindrical reflective support(reflector) 44 having a mirror-finished inner surface is set upright ona bottom wall of the processing vessel 42. A stage 46 for supporting asemiconductor wafer W, i.e., an object to be processed, thereon issupported on the reflective support 44. The reflective support 44 isformed of a material which can transmit heat rays, such as quartz. Thestage 46 has a thickness on the order of 1 mm, and is formed of acarbonaceous material or an aluminum compound, such as AlN.

[0033] A clamping ring 47, i.e., an object-to-be-processed holdingmember, for pressing down a peripheral part of the wafer W and fixingthe wafer W onto the stage 46 is supported above a peripheral part ofthe stage 46. The clamping ring 47 will be described later.

[0034] A transparent window 48 made of a material which can transmitheat rays, such as quartz, is hermetically joined to a portion of thebottom wall of the processing vessel 42 right under the stage 46. Aheater case 50 defining a heating chamber is joined to the bottom wallof the processing vessel 42 so as to surround the transparent window 48.A heating unit placed in the heater case 50 includes a plurality ofheating lamps 52, and a reflecting rotary table 54 serving also as areflector and supporting the heating lamps 52. The rotary table 54 isdriven for rotation via a shaft attached thereto by a motor 56 held at abottom wall of the heater case 50. Heat rays emitted by the heatinglamps 52 can travel through the transparent window 48 and fall on alower surface of the stage 46 to heat the same. A resistance-heatingelement embedded in the stage 46 may be used instead of the heatinglamps 52 for heating the stage 46.

[0035] A circular current-straightening plate 58 provided with aplurality of straightening holes 56 is disposed so as to surround anoutside periphery of the stage 46. The current-straightening plate 58 issupported on a circular column 60. A circular attachment 62 made ofquartz is placed on an inner peripheral part of thecurrent-straightening plate 58. Then, an outer peripheral part of theclamping ring 47 is adapted to come into light contact with an innerperipheral part of the attachment 62. An exhaust port 64 is formed in aportion of the bottom wall below the current-straightening plate 58. Anexhaust line 66 connects the exhaust port 64 to a vacuum pump, notshown, that can evacuate the processing vessel 42 to create a vacuum. Agate valve 68 is incorporated into a side wall of the processing vessel42. The gate valve 68 is opened when carrying a wafer W into and outfrom the processing vessel 42.

[0036] A showerhead 70 for introducing process gases or the like intothe processing vessel 42 is incorporated into a top wall of theprocessing vessel 42 opposite to the stage 46. More specifically, theshowerhead 70 has a body 72 formed of aluminum or the like and havingthe shape of a cylindrical box. A gas inlet 74 is formed in a top wallof the body 72.

[0037] The gas inlet 74 is connected to gas sources, not shown, whichrespectively supply necessary process gases, such as WF₆, Ar, SiH₄, H₂,N₂ and such. Respective flow rates of those process gases arecontrollable.

[0038] A bottom wall of the body 72 is provided with many gas-jettingholes 76. The gas jetting holes 76 are distributed over the entirebottom wall in order to jet gases supplied into the body 72 to aprocessing space S, and hence over the entire surface of the wafer Wmounted on the stage 46.

[0039] A diffusing plate 80 provided with many diffusing holes 78 isplaced in the body 72 in order to supply the gases much evenly over thesurface of the wafer W mounted on the stage 46.

[0040] As shown in FIG. 2, a plurality of, for example three L-shapedlifting pins 84 are attached at substantially equal angular intervals toan annular lifting ring 82, which is arranged below the stage 46, viarespective elastic-member covers 96. Upper parts of the lifting pins 84extend upright. The lifting pins 84 are vertically movable together withthe lifting ring 82. That is, the lifting pins 84 can be verticallymoved upward so that the upper parts thereof pass through holes 86formed in the stage 46 and can come into contact with the lower surfaceof the wafer W to lift up the wafer W. The lifting pins 84 can be alsomoved downward to lower the wafer W onto the stage 46. Lower parts ofthe lifting pins 84 extend through slots 85 formed in the reflectivesupport 44 and are capable of vertically moving in the slots 85. Alifting rod 88 connected to the lifting ring 82 extends through anopening formed in the bottom wall of the processing vessel 42, and alower end of the lifting rod 88 is connected to an actuator 92. Theopening of the bottom wall of the processing vessel 42 is covered with abellows 90. The bellows 90 allows the lifting rod 88 to move verticallyand seals the processing vessel 42 hermetically. A substantiallycircular (annular) clamping ring 47, whose shape conforms to an outlineof the wafer W, is disposed above a peripheral part of the stage 46 topress a peripheral part of the wafer W fixedly against the stage 46. Theclamping ring 47 is formed of, for example, a ceramic material. Aplurality of, for example three rods 94 are attached at substantiallyequal angular intervals to the clamping ring 47, i.e., anobject-to-be-processed holding member, so as to extend verticallydownward. The rods 94 are supported by the lifting ring 82 via therespective elastic-member covers 96, which are a feature of the presentinvention.

[0041] More specifically, as shown in FIGS. 3A to 3C, each of theelastic-member covers 96 is made of a transparent, corrosion-resistant,low heat-conductive material, such as quartz, and has a substantiallycylindrical shape. The elastic-member cover 96 is provided with a guidehole 98 of a diameter slightly greater than that of the rod 94 forguiding a vertical movement of the rod 94, in an upper part thereof, anda spring containing hole 100 of a diameter greater than that of theguide hole 98, in a lower part thereof. The guide hole 98 and the springcontaining hole 100 are communicated. The rod 94 is extended through theguide hole 98 and the spring containing hole 100. A coil spring 102,i.e., an elastic member, is placed in the spring containing hole 100 soas to surround a lower part of the rod 94. Then, the coil spring 102 iscompressed between a spring stopper 104 formed at a lower end of the rod94 and an upper end surface 100A of the spring containing hole 100 inorder to give downward force to the clamping ring 47 at all times.

[0042] Thus, each of the coil springs 102 is substantially entirelycovered with the elastic-member cover 96, excluding a lower partthereof.

[0043] Stopping projections 106 project from upper ends of theelastic-member covers 96, respectively, to limit the downward movementof the clamping ring 47 relative to the elastic-member covers 96.

[0044] The edge 98A of each guide hole 98 is beveled (tapered) orrounded to ensure that the rod 94 can smoothly move therethrough.

[0045] A process, such as a film deposition process, to be carried outby this processing apparatus will be described by way of example.

[0046] The gate valve 68 on the side wall of the processing vessel 42 isopened, a carrying arm (not shown) carries a wafer W into the processingvessel 42, the lifting pins 84 are raised, and the wafer W istransferred from the carrying arm onto the lifting pins 84 as shown inFIG. 3A. Subsequently, the lifting pins 84 are lowered to mount thewafer W on the stage 46 as shown in FIG. 3B. As the lifting pins 84 arelowered further, the clamping ring 47 comes into contact with aperipheral part of the wafer W. As the lifting pins 84 are lowered stillfurther, the coil springs 102 are further compressed as shown in FIG.3C. Consequently, the peripheral part of the wafer W is pressed down byresilience of the coil springs 102 so that the wafer W is fixedly heldon the stage 46. In this state, the compressed coil springs 102 arecompletely contained in the spring containing holes 100, that is, areentirely covered with the elastic-member covers 96, respectively.

[0047] Suppose that a tungsten film is to be deposited on the wafer W.Process gases optionally including some or all of WF₆ gas (source gas),SiH₄ gas, H₂ gas (reducing gas), Ar gas, N₂ gas (diluting gas) or thelike are supplied at predetermined flow rates, respectively, into theshower head 70. A mixture of those process gases is jetted substantiallyuniformly into the processing vessel 42 through the gas jetting holes 76formed in the bottom wall of the body 72 of the showerhead 70. At thesame time, an atmosphere in the processing vessel 42 is exhaustedthrough the exhaust port 64 to create and maintain a predeterminedvacuum in the processing vessel 42, the rotary table 54 supporting theheating lamps 52 thereon and disposed below the stage 46 is rotated, andthe heating lamps 52 are energized to make the same radiate thermalenergy.

[0048] Heat rays emitted by the heating lamps 52 travel through thetransparent window 48 and fall on the back surface of the stage 46 toheat the same. Since the stage 46 has a very small thickness on theorder of 1 mm, the stage 46 can be quickly heated. Consequently, thewafer W mounted on the stage 46 can be quickly heated to a predeterminedtemperature. The process gases supplied into the processing vessel 42undergo predetermined chemical reactions to deposit (form) a tungstenfilm on the surface of the wafer W according to a film depositioncondition. N₂ gas or Ar gas, as a so-called backside gas, is suppliedinto a space around the backside of the stage 46.

[0049] One or some highly corrosive process gases including the WF₆ gasmay flow around the stage 46 into the space around the backside of thestage 46 in addition to the processing space S in the processing vessel42, during this film deposition process. However, the coil springs 102made of a metal are exposed scarcely to the corrosive gases and hencecorrosion of the coil springs 102 is prevented, because the coil springs102 are substantially entirely contained in the spring containing holes100, that is, because the coil springs 102 are covered substantiallycompletely with the elastic-member covers 96.

[0050] In the embodiment, since the elastic-member covers 96 are made ofa material having an excellent corrosion resistance and a low thermalconductivity, corrosion of the elastic-member covers 96 can be alsoprevented. In addition, the elastic-member covers 96 can suppress riseof temperature of the coil springs 102 and hence the coil springs 102can be contained in a less corrosive environment.

[0051] Even if the coil springs 102 should be corroded and hencecorrosion products should scatter, the corrosion products can scatteronly downward because only lower ends of the spring containing holes 100are open. Thus, it is scarcely possible that the scattered corrosionproducts contaminate the wafer W mounted on the stage 46.

[0052] Each rod 94 may be formed in such a length that the springstopper 104 supporting the lower end of the coil spring 102 can bealways completely contained in the spring containing hole 100 and thatthe lower end of the spring containing hole 100 may be completelyclosed, which can prevent the exposure of the coil springs 102 to thecorrosive gases more effectively.

[0053] This effect on controlling the corrosion of the coil springs 102is effective also in a cleaning process wherein a highly corrosivecleaning gas is supplied into the processing vessel 42 for cleaning.

[0054] The elastic-member covers 96 may be formed of a ceramic material,such as Al₂O₃, having functions substantially similar to those ofquartz.

[0055] The object to be processed is not limited to a semiconductorwafer, and the present invention is applicable to an LCD substrate, aglass substrate or the like.

What is claimed is:
 1. A processing apparatus comprising: a processingvessel in which a vacuum can be created; a stage disposed in theprocessing vessel for supporting an object to be processed thereon; aclamping member supported above the stage and capable of pressing down aperipheral part of the object to be processed mounted on the stage tofixedly hold the object to be processed on the stage; an elastic memberfor giving a force to cause the clamping member to press down theperipheral part of the object to be processed mounted on the stage; andan elastic-member cover substantially entirely covering the elasticmember.
 2. A processing apparatus according to claim 1, wherein theelastic-member cover is highly corrosion-resistant.
 3. A processingapparatus according to claim 1, wherein the elastic-member cover is madeof a material having a low thermal conductivity.
 4. A processingapparatus according to claim 1, wherein the clamping member has a rodextending downward from a lower surface thereof, the elastic member is acoil spring surrounding the rod, the rod is provided with a springstopper at a lower end thereof to support a lower end of the coil springthereon, and an upper end of the coil spring rests on a clamping-membersupporting member through which the rod extend and which can support alower surface of the clamping member.
 5. A processing apparatusaccording to claim 4, wherein the elastic-member cover is formedintegrally with the clamping-member supporting member.
 6. A processingapparatus according to claim 5, wherein the elastic-member cover alsocovers the lower end of the rod and the spring stopper.
 7. A processingapparatus according to claim 4, wherein the clamping-member supportingmember is formed integrally with lifting pins capable of moving throughthe stage and of vertically moving the object to be processed on thestage.
 8. A processing apparatus according to claim 1 furthercomprising: a process-gas supply means for supplying a process gas intothe processing vessel; and a heating means for heating the object to beprocessed mounted on the stage.